These days, the internet is widely spread, and as many pieces of information as called a sea of information are now provided through the internet. There are many cases where a search service is used when finding information desired by us among numerous pieces of information provided through the internet.
There are several search methods for providing such a search service. First, there is a method of sequentially searching words from the first to the last in existing database. In other words, even if the first word has been found in the database, the same word may be also present in the sentence; therefore, the search has to be performed throughout the sentence by comparing every word up to the end of the sentence.
This method suffers from a disadvantage that it may take a lot of time to find a particular word.
In addition, there is a method of arraying words as in a dictionary and finding a desired word by hash index. In other words, a position of main sentence is found by defining a hash value corresponding to a word and positioning the value at a particular position to thereby narrow a search range.
This method suffers from a disadvantage that the hash has to be newly arrayed whenever a new word is added.